Living cells are known to exhibit unusual mechanical properties including an internal nonlinear stiffening under external stress, in which their stiffness can increase by orders of magnitudes [1]}, reversible softening under compression [2]}, viscoplasticity [3]} and poroelasticity [4]}. A long-standing puzzle is related to the surprisingly slow stress relaxation that has been measured in living cells.
This stress relaxation reveals more than just a long relaxation time, but also a broad spectrum of relaxation times, with
a dynamic modulus that varies with frequency as a power-law with exponent \(\beta \)  in the range of \(\sim 0.1- 0.3\)  [5]}.
It has been argued that this may be related to the soft glassy rheology (SGR) model [6]}, [5]}, [8]}, although the relevance and validity of this in cell mechanics remains unclear.
